Method for estimating transmission input torque
Patent 7370516 Issued on May 13, 2008. Estimated Expiration Date: 
November 21, 2025. Estimated Expiration Date is calculated based on simple USPTO term provisions. It does not account for terminal disclaimers, term adjustments, failure to pay maintenance fees, or other factors which might affect the term of a patent.
November 21, 2025. Estimated Expiration Date is calculated based on simple USPTO term provisions. It does not account for terminal disclaimers, term adjustments, failure to pay maintenance fees, or other factors which might affect the term of a patent.Patent ReferencesFluid pressure sensor with temperature indication Control for a motor vehicle drive having an automatic transmission Line pressure optimization in an automatic transmission Line pressure control device for continuous transmission in vehicle Patent #: 6530860 InventorAssigneeApplicationNo. 11285487 filed on 11/21/2005US Classes:73/117.2, Disparate tests under operating conditions73/116, MOTOR AND ENGINE TESTING73/117.3, With continuous operation374/143, Pressure477/109, Diminution during transmission change477/115, Transmission controlled by engine477/45, Fluid pressure control477/156, Transmission pressure controlled701/54, Engine output control477/39, With clutch control701/51Transmission controlExaminersPrimary: Cygan, MichaelAssistant: Dunlap, Jonathan Foreign Patent References
International ClassesG01M 15/00G01L 5/00 DescriptionTECHNICAL FIELDThe present invention is drawn to a method for estimating the transmission input torque of a vehicle. BACKGROUND OF THE INVENTION It is well known to estimate a vehicle's transmission input torque based on engine throttle position. The estimated transmission input torque values may be implemented, for example, to calculate shift schedules, clutch pressure, clutchapply/release rates, etc. Any imprecision in the estimated transmission input torque value can therefore cause shift aberrations such as improperly timed shifts, short shifts, long shifts, etc. SUMMARY OF THE INVENTION The present invention provides a method for precisely estimating the transmission input torque of a vehicle. The method includes identifying a plurality of measurable characteristics that influence transmission input torque. According to apreferred embodiment, the measurable characteristics include torque converter clutch input speed, torque converter clutch slip speed, transmission oil temperature, and torque converter clutch apply pressure. Thereafter, transmission input torque valuesare measured on a sample powertrain operating at a plurality of different combinations of the measurable characteristics. The torque measurements are preferably obtained in a test lab using a sample powertrain having components substantially similar tothose of the particular vehicle to which the method of the present invention is being applied. A look-up table including the measured input torque values corresponding to each combination of the measurable characteristics is established and saved onto a vehicle memory device. The vehicle is configured to implement a control module and aplurality of sensors adapted to monitor the measurable characteristics as the vehicle is operated. At any given time, the vehicle control module can retrieve from the look-up table the measured transmission input torque value that most closelycorresponds to the current status of the monitored measurable characteristics, wherein the measured transmission input torque value provides an estimate of the actual transmission input torque of the vehicle. This retrieved value may then be used forcalculating shift schedules, clutch pressure, clutch apply/release rates, etc. The above features and advantages and other features and advantages of the present invention are readily apparent from the following detailed description of the best modes for carrying out the invention when taken in connection with theaccompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram of a vehicle according to the present invention; and FIG. 2 is flow chart illustrating a method of the present invention. DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the drawings, wherein like reference numbers refer to like components, FIG. 1 schematically shows a vehicle 10 having a powertrain 12 which includes an engine 14, a transmission 16, and a torque converter 18. The transmission 16includes a transmission control module 20, or TCM 20, having a memory storage device 21, and a transmission oil temperature sensor 22. It should be appreciated that the vehicle 10 and powertrain 12 are shown for exemplary purposes and that the method ofthe present invention is also applicable to alternate vehicle/powertrain configurations. The torque converter 18 includes an impeller 24 (a driving member), a turbine 26 (a driven member), and a torque converter clutch 28, or TCC 28. The TCC 28 is preferably a slipping type torque converter clutch, however, it should be appreciatedthat the present invention may also be applied to other types of torque converter clutches. The torque converter 18 further includes a housing member (not shown) attached to the impeller 24 such that a chamber full of working fluid (not shown) is formedtherebetween. The impeller 24 is connected to a crankshaft of the engine 14, and engine torque is transmitted from the impeller 24 to the turbine 26 through an operation of the working fluid. The turbine 26 is connected to an input shaft of the transmission16 to transmit the engine torque to the transmission 16. The TCC 28 includes a first clutch member 30 attached to the turbine 26, and a second clutch member 32 attached to the impeller 24. The TCC 28 is configured to selectively engage the first and second clutch members 30, 32 to lock the turbine 26and impeller 24 so that they rotate as a single member. When the TCC 28 is engaged, there is not torque loss through the torque converter 18 such that the efficiency of the powertrain 12 is optimized. The TCC 28 is preferably hydraulically engaged by aconventional hydraulic device such as the hydraulic actuator 34. A turbine speed sensor 36 is attached to the turbine 26 and is configured to measure the rotational speed of the turbine 26. It should be appreciated that, because the first clutch member 30 is attached to the turbine 26, the rotational speed ofthe turbine 26 is also the torque converter clutch output speed Vo. An impeller speed sensor 38 is attached to the impeller 24 and is configured to measure the rotational speed of the impeller 24. It should be appreciated that, because the secondclutch member 32 is attached to the impeller 24, the rotational speed of the impeller 24 is also the torque converter clutch input speed Vi. Additionally, the torque converter clutch slip speed Vs can be calculated according to the equation Vs=Vi-Vo. Apressure sensor 40 is attached to the TCC 28 and is configured to measure the torque converter clutch apply pressure. The torque converter clutch apply pressure is a measure of the hydraulic pressure transferred to the TCC 28 by the hydraulic actuator34. Referring to FIG. 2, a method 50 for estimating the transmission input torque of the vehicle 10 (shown in FIG. 1) is shown. It should be appreciated that the blocks labeled 52-62 represent steps performed in accordance with the method 50. At step 52, a plurality of measurable characteristics that influence transmission input torque are identified. According to a preferred embodiment of the present invention, there are four measurable characteristics A, B, C and D, respectivelyrepresenting torque converter clutch input speed; torque converter clutch slip speed; transmission oil temperature; and torque converter clutch apply pressure. At step 54, transmission input torque values are measured on a powertrain operating at a plurality of different combinations of the measurable characteristics A-D. The transmission input torque values are preferably measured using a conventionaltorquemeter 55 (as shown in FIG. 1) attached to the input shaft of a transmission. As conventional torquemeters apply resistance to obtain torque readings, they reduce the efficiency of the system to which they are applied and are therefore not apractical solution for obtaining transmission input torque values of a production vehicle. Accordingly, the torque measurements are preferably obtained in a test lab using a sample powertrain, or multiple powertrains, having components substantiallysimilar to those of the particular vehicle to which the method 50 is being applied. For example, by measuring transmission input torque values on a sample powertrain having components substantially similar to those of the powertrain 12, the measuredtorque values from the sample powertrain should be similar to the actual torque values of the vehicle 10. At step 56, a look-up table T is established. The look-up table includes the measured input torque values corresponding to each combination of the measurable characteristics A-D. At step 58, the look-up table T is recorded onto a memory deviceof the vehicle 10 (shown in FIG. 1). According to a preferred embodiment, the look-up table T is recorded onto the memory storage device 21 of the TCM 20. At step 60, the measurable characteristics A-D are monitored during vehicle operation. According to a preferred embodiment, the measurable characteristics A-D are monitored by the TCM 20 (shown in FIG. 1) in conjunction with the sensors 22, 36,38, and 40 (shown in FIG. 1). More precisely, the measurable characteristic A representing torque converter clutch input speed Vi is obtained from the speed sensor 38. The measurable characteristic B representing torque converter clutch slip speed Vsis obtained according to the equation Vs=Vi-Vo, where Vi is obtained from sensor 38 and Vo is obtained from sensor 36. The measurable characteristic C representing the transmission oil temperature is obtained from sensor 22. The measurablecharacteristic D representing the torque converter clutch apply pressure is obtained from sensor 40. The data recorded by the sensors 22, 36, 38, and 40 is transferred to the TCM 20 so that at any given time, the current status of the measurablecharacteristics A-D may be obtained. At step 62, the measured transmission input torque value that most closely corresponds to the current values of the measurable characteristics A-D is retrieved from the look-up table T. According to a preferred embodiment, the TCM 20 (shown inFIG. 1) retrieves the measured transmission input torque value from the memory 21 (shown in FIG. 1). The measured transmission input torque value retrieved from the look-up table T represents an estimate of the actual transmission input torque of thevehicle 10 (shown in FIG. 1) which may be used for calculating shift schedules, clutch pressure, clutch apply/release rates, etc. While the best modes for carrying out the invention have been described in detail, those familiar with the art to which this invention relates will recognize various alternative designs and embodiments for practicing the invention within thescope of the appended claims. |
